Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
In a typical market area, wireless service providers may operate radio access networks (RANs) each arranged to provide user equipment devices (UEs) with wireless communication service. Each such a RAN may include a number of base stations that radiate to define wireless coverage areas in which to serve UEs according to a radio access technology such as Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Operability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1xRTT and 1xEV-DO), GSM, GPRS, UMTS, EDGE, iDEN, TDMA, AMPS, MMDS, WIFI, and BLUETOOTH, or others now known or later developed. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station or by other base stations.
A wireless service provider may operate one or more such RANs as a public land mobile network (PLMN) for serving UEs. For example, a service provider may operate an LTE RAN as a PLMN for serving UEs with LTE service. In general, each such PLMN may have a respective PLMN identifier (PLMNid), and UEs that subscribe to service of the PLMN may be provisioned with data indicating that PLMNid. For instance, the UE may maintain in data storage a terminal identifier that uniquely identifies the UE and that includes an indication of the PLMNid to which the UE subscribes, such as an international mobile subscriber identity (IMSI) that includes as its first six digits the PLMNid. Further, the UE may be provisioned with program logic that causes the UE to provide an indication of its PLMNid to a base station when the UE seeks to be served by the base station, such as to provide the base station with the UE's IMSI including the UE's PLMNid.
(Note also that some radio access technologies may use other terms to characterize the service provider's network to which UEs may subscribe, and those other networks could be considered types of PLMNs for purposes of this disclosure even though they are characterized by other terms. For instance, CDMA identifies a service provider's network by a combination of system identifier and network identifier (SID/NID). Other examples are possible as well.)
In addition to operating a RAN as its own PLMN (home PLMN) for serving its own subscriber UEs, a wireless service provider may also operate a RAN on behalf of one or more other wireless service providers known as “mobile virtual network operators” (MVNOs), to allow the MVNOs to provide wireless communication service without the need to build out RANs of their own. (In practice, an MVNO may be a different company than the actual RAN operator or may be the same company as the actual RAN operator.) In this arrangement, the MVNO may be considered to provide an MVNO PLMN, which may have its own PLMNid. However, the wireless service provider would in fact be operating its RAN not only as its own PLMN but also as the MVNO's PLMN. In addition, a wireless service provider that functions as an MVNO using the RAN of another service provider may also operate its own RAN in certain locations, and may in fact host service for the other service provider in certain locations, such that the other service provider would then function as an MVNO in those locations.
Still further, a wireless service provider may have roaming agreements with other wireless service providers, to provide a wider range of coverage for UEs. In such arrangements, a UE that subscribes to service of a service provider's PLMN but is not within sufficient coverage of that service provider's RAN may instead be served by another service provider's RAN, and the service providers may work with each other to account for the costs of that roaming service. In that case, from the perspective of the serving RAN, the UE would be a subscriber of a roaming partner PLMN.
In practice, base stations of a given RAN may therefore provide service for possibly multiple PLMNs. For instance, a base station operated by a wireless service provider may provide service for a PLMN of that service provider and may also provide service for PLMNs of one or more MVNOs, as well as PLMNs of one or more roaming partners.
In an ideal arrangement, the base stations of a wireless service provider's RAN would provide seamless coverage throughout the market area, so that UEs being served by the system could move from coverage area to coverage area without losing connectivity. In practice, however, it may not be possible to operate a sufficient number of base stations or to position the base stations in locations necessary to provide seamless coverage. As a result, there may be holes in coverage.
One way to help to resolve this problem is to operate a relay node that extends the range of a base station's coverage area so as to partially or completely fill a coverage hole. Such a relay node may be configured with a wireless backhaul interface for communicating with and being served by the base station in much the same way that a UE does, and a wireless access interface for communicating with and serving one or more UEs in much the same way that a base station does. Further, the relay node may include control logic for actively bridging the backhaul communications with the access communications. The relay node may thus receive and recover downlink communications from the donor base station and transmit those communications to the UEs served by the relay node, and may likewise receive and recover uplink communications from UEs served by the relay node and transmit those communications to the base station.
In this arrangement, the base station is considered a to be “donor base station,” in that the base station provides coverage to the relay node and the relay node then provides coverage to one or more UEs. In practice, the wireless communication link between the donor base station and the relay node is considered to be a “relay backhaul link,” and the wireless communication link between the relay node and UEs served by the relay node is considered to be a “relay access link.” Further, to the extent the base donor station itself also serves UEs, the wireless communication link between the donor base station and those UEs is considered to be a “donor access link.”
Advantageously, a relay node like this might have a relatively small form factor, with antenna height lower than the base station and with reduced transmit power requirements and cost. Consequently, a wireless service provider may conveniently employ such relay nodes throughout a region to help efficiently fill coverage holes and improve service quality.